The correct answer is 186. When multiplying 31 by 6, we can use the method of long multiplication. We multiply 6 by the ones digit of 31, which is 1, and get 6. Then we multiply 6 by the tens digit of 31, which is 3, and get 18. We write down the 8 and carry over the 1 to the next column. Finally, we multiply 6 by the hundreds digit of 31, which is 0, and add the carried over 1, resulting in 1. So, the final answer is 186.